Can your employer terminate you or try to demote you due to medical restricted duty? I am working 24 hr a wk.

i had a car accident that messed up my back. was off 5 mo. went back to work gradually. 16, 20, now at 24hrs per wk.. My job is now saying they are looking to hire a person and phase out my position and that if I get better in the next 1-2 mo., they said I can apply for it or work under that person. I would no longer be a supervisor. they also said maybe I could work in another department doing work that i personally feel I am not experienced to do. I have worked there since 1991. (16) years faithfully & never had sick leave before. Since I have been back to work, I have been doing my job as supervisor, but not able to stand more than 1-2 hrs. I am also doing work that was not under my job description, due to them not filling a position that was vacated. I am getting so much more paper work done, but because i am working only 24hrs they feel I am not fufilling the job description. Do I have legal recourse?